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Plasmid-Mediated AmpC β-Lactamase CITM and DHAM Genes Among Gram-Negative Clinical Isolates
Subhas Chandra Aryal1, Milan Kumar Upreti1, Anil Kumar Sah2
1Golden Gate International College, Kathmandu, Nepal.
Background:
Antibiotic resistance mediated by the production of extended-spectrum β-lactamases (ESBLs) and AmpC β-lactamases is posing a serious threat in the management of the infections caused by Gram-negative pathogens. The aim of this study was to determine the prevalence of two AmpC β-lactamases genes, bla CITM and bla DHAM, in Gram-negative bacterial isolates.
Materials And Methods:
A total of 1151 clinical samples were obtained and processed at the microbiology laboratory of Annapurna Neurological Institute and Allied Science, Kathmandu between June 2017 and January 2018. Gram-negative isolates thus obtained were tested for antimicrobial susceptibility testing (AST) using Kirby-Bauer disk diffusion method. AmpC β-lactamase production was detected by disk approximation method using phenylboronic acid (PBA). Confirmed AmpC β-lactamase producers were further screened for bla CITM and bla DHAM genes by conventional polymerase chain reaction (PCR).
Results:
Out of 1151 clinical specimens, 22% (253/1152) had bacterial growth. Of the total isolates, 89.3% (226/253) were Gram-negatives, with E. coli as the most predominant species (n=72) followed by Pseudomonas aeruginosa (n=41). In the AST, 46.9% (106/226) of the Gram-negative isolates were multidrug resistant (MDR). In disk diffusion test, 113 (50%) isolates showed resistance against cefoxitin, among which 91 isolates (83 by disk test and Boronic acid test, 8 by Boronic test only) were confirmed as AmpC β-lactamase-producers. In PCR assay, 90.1% (82/91) and 87.9% (80/91) of the isolates tested positive for production of bla CITM and bla DHAM genes, respectively.
Conclusions:
High prevalence of AmpC β-lactamase-producers in our study is an alarming sign. This study recommends the use of modern diagnostic facilities in the clinical settings for early detection and management which can optimize the treatment therapies, curb the growth and spread of the drug-resistant pathogens.
Insights
Antibiotic resistance from AmpC β-lactamase-producing Gram-negative bacteria is a significant threat. This study found a high prevalence of these resistance genes in clinical isolates, necessitating improved diagnostics and management strategies.
Area of Science:
- Microbiology
- Molecular Biology
- Clinical Diagnostics
Background:
- Extended-spectrum β-lactamases (ESBLs) and AmpC β-lactamases contribute to antibiotic resistance in Gram-negative pathogens.
- The increasing prevalence of these enzymes poses a serious challenge for treating bacterial infections.
Purpose of the Study:
- To determine the prevalence of two specific AmpC β-lactamase genes, blaCITM and blaDHAM, in Gram-negative bacterial isolates.
- To assess the rate of AmpC β-lactamase production in clinical samples.
Main Methods:
- Collected and processed 1151 clinical samples.
- Performed antimicrobial susceptibility testing (AST) and disk approximation tests for AmpC β-lactamase detection.
- Utilized polymerase chain reaction (PCR) to screen for blaCITM and blaDHAM genes.
Main Results:
- 22% of clinical specimens yielded bacterial growth, with 89.3% being Gram-negative isolates.
- 46.9% of Gram-negative isolates were multidrug resistant (MDR).
- 91 isolates were confirmed as AmpC β-lactamase producers, with high detection rates for blaCITM (90.1%) and blaDHAM (87.9%) via PCR.
Conclusions:
- The high prevalence of AmpC β-lactamase producers is an alarming finding.
- Recommends implementing advanced diagnostic tools for early detection and optimized treatment of drug-resistant infections.
- Emphasizes the need to control the spread of resistant pathogens.
